text: Carbenes can be stabilised as organometallic species. These transition metal carbene complexes fall into two categories:
  * Fischer carbenes in which carbenes are tethered to a metal and an electron-withdrawing group (usually a carbonyl),
  * Schrock carbenes; in which carbenes are tethered to a metal and an electron-donating group. The reactions that such carbenes participate in are very different from those in which organic carbenes participate.